He admitted he was “appalled and ashamed” because he claimed the bombing of civilians went against everything it stood for.

He said the attacks on The Mulberry Bush and The Tavern in The Town had been in revenge for the death of IRA bomber James McDade.

At first he feared that the timing of the attacks - with very little warning - had been deliberate because “tempers were high”, reports the Birmingham Mail.

Admission: Former IRA senior officer Kieran Conway and the Tavern in the Town Pub (Image: Birmingham Mail)

But he was later told that the IRA unit involved had tried to use “a succession of phone boxes” which were out of order, significantly delaying the bomb-warning call.

Conway, who makes the admissions in his new memoir, also revealed that soon after the bombings the IRA’s England Operational Commander and his adjutant “made it back home” to Dublin for an urgent de-brief and to assess the impact of the disaster as far as the terrorists were concerned.

Funding for the terrorists dried up almost overnight and the bombings, which left 21 dead and almost 200 injured, including many maimed for life, cost them hugely in the propaganda war.

“And I hope that Mr Cameron, who a week ago told The House of Commons that the pub bombers must be found, takes note of this development and ensures that the police follow this through.”

Brian added: “The police keep saying they won’t do anything because there is no fresh evidence.

"Well, here it is in black and white. It’s an admission. They have got to do something with this information.”

Mr Conway, now a criminal lawyer in Dublin, says in the book that where off-duty soldiers were the targets of bombings: “I had little sympathy for either the soldiers or the unfortunate civilians who had been sharing their drinking space.”

He continued: “The Birmingham bombs were another matter.

"The bombings came after British police disrupted funeral arrangements for James McDade, a volunteer who had himself died in a premature explosion in England.

“Tempers were high and I, for one, certainly at first feared that the local IRA had knowingly caused these dreadful casualties – 21 people were killed and a great many others injured.”

Damage: Firemen survey the outside the Tavern in the Town on 22 November 1974 (Image: Getty)

“I was appalled and personally ashamed of the bombing, which went against everything we claimed to stand for.”

He said he told two other senior IRA figures, Dave O’Connell and Kevin Mallon “exactly what I thought” when they met up.

The first bomb destroyed The Mulberry Bush just six minutes later. The Tavern was destroyed at 8.27pm.

Conway was not directly involved in the debrief with the England Operational Commander.

But he said he was later told “that the early indications were that the casualties were the result of yet another failure in the warning system, a succession of phone boxes from which the warning might have been relayed having proved to be inoperable.”

In an interview with a national newspaper he described the Birmingham pub bombings as “a total disaster.”

He added that the secret ‘Feakle Talks’, held a couple of weeks after the bombings, were used by the IRA to try to start to repair its image after the Birmingham and the Guildford pub bombings.

The talks, in Feakle, County Clare, involved senior IRA officials and Protestant clergymen and ended abruptly after a tip-off that Irish Special Branch officers were on their way to arrest the republicans.

But they set in train a process that eventually led to a brief ceasefire that began on December 22, 1974.

Conway had been recruited in 1970, having been radicalised during the 1968 student protest movements.

He met with senior republicans, including future deputy first minister of Northern Ireland Martin McGuinness and Sinn Fein president Gerry Adams.

Conway was later jailed in Belfast’s notorious Crumlin Road prison and went on hunger strike to achieve political status.

Although he left the IRA in 1975, he rejoined during the 1981 hunger strike, then finally broke with the republican movement for good in 1993 when the British and Irish governments announced the Downing Street Declaration.

He claimed the declaration basically reinforced partition.

“The IRA went on ceasefire, it decommissioned and did all the things they said they would never do, and disappeared into history,” he said.

“It was a complete and utter defeat, absolutely.”

In his book he also claims that rogue Irish police officers colluded with the IRA throughout the Troubles and that members of the Dublin establishment, including several mainstream politicians, aided the Provisionals in their armed campaign.